A Proper Barrel Fire: A secure way to dispose of data storage

This post is inspired by post by Bruce Scheier and Mircea Popescu on things that are not air gapping and things that are air gapping. In Mircea's article he mentions his method of oxidizing hard disk platters by boiling them in tomato sauce. It seems like a solid method for chemically rendering used platters unrecoverable. In the comments to the article I mentioned that a proper barrel fire seems like a reasonable proposal for handling the destruction of solid state media. Since USB sticks are a thing, and there are differences between any given barrel fire and a proper barrel fire.

The first, and one of the more important steps is selecting the right barrel. A 55 gallon drum for this purpose is the wrong barrel. The right barrel is the one from a laundry washing machine. The numerous holes in it are great for air flow, and spending the time to equivalently perforate a 55 gallon drum to similarly feed your fire oxygen is a lot of work. We use a barrel, as opposed to an uncontained fire like a bond fire, because the metal walls retain and reflect much of the heat inward which is valuable when we want to oxidize and melt things. The idea here is to produce a lot of heat for a lot of time. With this barrel you will probably want a bare steel wheel from a car, truck, or trailer to set it on so as to avoid scorching the ground. Edit: If you want to destroy a few USB sticks or SD cards make an event of it. If you want to destroy any circuit boards like hard drive PCBs or hard drive sized SSDs you probably want to do this away from civilization.

As you are only trying to destroy some property It is probably best to set this whole thing up on a concrete or gravel pad giving it a ten or more foot radius from anything else. You also want nothing above it, either directly or up and at some angle for quite a distance. Where airplanes fly is probably safe. Where powerlines, trees, and awnings live is not safe. If you attempt this indoors, a Mister Darwin would probably like to meet you.

Now, gather the data storage devices you want to dispose of. Start disassembling them. For hard drives this means getting the platters out. For USB and other flash drives it means getting the case off and getting to the circuit board1. Once everything is dissassembled separate everything into three piles. The first pile is cruft that is known to be incapable of storing data like cases. The second is stuff that might conceivably store data like the hard drive's PCB. The third pile is stuff that is known to have stored data like the NAND chips in flash memory and the hard drive's platters. Set aside the first pile for now and place the second and third piles into bags. Set the bags on a hard concrete surface, center your mind and find your angry place, and savage the bags and their contents with a hammer. At any point should a bag be breached recover any spilled contents into the bag and either patch the bag or put it in another bag.

After no less than ten minutes examine the contents of the bag. Is everything good and smashed? If it is you can start building your fire. Begin by making layer of charcoal briquettes roughly 3 deep on the bottom of your barrel. This layer of charcoal is going to make sure there's a consistent source of heat available throughout the whole barrel should some of your hardware bits fall down, the charcoal will make sure they continue to be exposed to consistent, destructive heat. Next you lay down two split logs2 parallel to each other. Between these logs is where the bags go. Throw some anthracite 3 coal pellets into the bags with the storage media, then lay the bags between these logs. Now over up the bags with some kindling sized wood and more split logs.

Once the bags are obscured from view call up some close friends to come over because you are hosting a fire, providing you aren't burning much in the way of circuit board. No so many or the wrongs kinds such that a disturbance might be caused, but a few so that your blazing inferno has the pretense of a being a social gathering and not the product of some loner who just wanted to make an incredible fire. Continue building the fire as you wait for people to arrive. When your laundry barrel is full of fuel and an audience has arrived sprinkle it generously with kerosene sprinkle it with kerosene4 and manage to safely light it somehow.

As the data fire grows start a second fire in your shitty charcoal grill, cook some meat and be a gracious host. As the fire burns down add more fuel logs to the fire keeping it well fed. While social events surrounding fire may be well associated with intoxication, your mission is to avoid excess inebriation while you make sure that there are 6 to 8 hours of intense burning.5 Maybe at some point you let the fire cool a bit so people can roast marshmallows and weiners, but you build it back up afterwards. Your goal is maximizing heat and time.

The next morning or afternoon, sometime roughly 8 to 12 hours after you began letting the fire burn to its end, you check your fire barrel stirring through the ashes. You are looking for coals that are still hot as well as identifiable computer parts. Ideally you may find some unidentifiable melted clumps, but a surprising amount of material should be missing rendered into ash and smoke. Douse the ashes in water to make sure any material that remain burning is out, then you dispose of the ashes as is customary. Any identifiable bits that have not been melted to the inside of the barrel should be moved to the pile with things that could not have stored data. Put this last pile into yet another bag and discretely dispose of it in some well trafficked public restroom's trash can.

Commentary is welcome as are suggestions for improvement. Criticism is welcome too.

Extra credit if you can identify the actual memory and separate it. [↩]

The primary fuel for this fire should be split seasoned hardwood logs. You will want a lot of them. [↩]

Anthracite because the aesthetic being sought is campfire and not trash fire [↩]

Gasoline is the wrong accelerant to use. Even if you think this is the kind of data worth protecting with a cyanide pill. [↩]

This implies that you should have acquired a substantial woodpile to burn from. [↩]

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9 Responses to “A Proper Barrel Fire: A secure way to dispose of data storage”

I have yet to try it for more than two usb sticks, an SD Card, and a 2.5" platter. I have yet to attempt the expanded version of this to include any hard drive PCB's, but I could see attempting this exercise not scaling very well for the destruction of too many things.

The hard drive PCB might be too much for civilized areas and peoples as may a hard drive sized SSD. For two PNY 8GB mini attaches, a 1 GB Polaroid branded secure digital card, and the platter there wasn't much unusual smell for any substantial duration in time.

@Stanislav Datskovskiy It'll probably only stink for the first 10-15 minutes or so.

It's kind of difficult to evaluate his method without actually prototyping it, but PCBs can be cleanly burned both as a point of theory (if the process is hot enough the various aromatic compounds liberated in the smoke will eventually be broken down to the ultimate h2o and co2 dual fate of all organics) and in fact (as plenty of places have working incinerators).

I have since tested with more hard drive platters, they seems to leave a crusty residue in the ashes similar to what happens when one allows a similar fire to dispose of one's beer bottles. Metallic parts similarly tend to leave metallic clumps in the ash, unless you burden the fire with an excessive thermal mass of metal parts. The mass of the cooled post burn clumps was less than the mass of metal and glass I put into it, even with the ash mixed into the clumps, suggesting a good portion of material was sent into the air.

Anyways it would probably be irresponsible to invite people to a fire like this, unless you invite them to destroy data storage media too. I have yet to test another PCB since the ill fated attempt to scorch one with the butane torch in the garage.

A sustained hardwood fire in appropriate container with a little bit of an anthracite coal kicker seems a perfectly reasonable means to destroy many forms of storage media not explicitly designed to resist it. I suggest hardwood over (regionally) cheaper softwoods because the greater thermal density allows higher temperatures. I recommend the laundry machine barrel, because well... I have yet to see a container that sustains greater temperature for a wood fire.

This method might not be reasonable for everyone, but for many it is more accessible than oil of vitrol or aqua regia, and probably less carcinogenic in its waste products.